Is 245/40/18 a no go?

[s2_bo]

The S8 i bought recently came with 245.40.18 and not 245.45.18 tires like its supposed to have.
They look a bit small as they dont fill out the arches as much..
Should i change them asap or is it ok to keep them on until they are on the wear indicators?

Thanks.
Bo

[Architex_mA8tey]

see the attached image
if they are all the same size then your speedo will just indicate you are doing faster than you actually are by 2.2mph and you can just wait until they are worn down to renew with a new size but again you will need to do all 4
if you have different sizes on front or back and quattro then you may get more of an issue!!

[s2_bo]

Thank you that's very useful info.
They are all the same size but the spare is 45.
Would it damage the diff to use one 45 on a set of 40s for a short period of time should i have a blow out?


Cheers.
Bo

[Architex_mA8tey]

I don't think it would damage the diff but the car would sense the differing wheel speeds and think you were encountering a slipping wheel situation so not sure what the electronics would make of that. :Confused:

[Adrian E]

It definitely wouldn't be recommended running the spare as it stands.

How much tread is left on the old ones?

[s2_bo]

The 40s have 5mm the spare has 3mm.

Thanks.
Bo

[Adrian E]

Might be worth seeing what you can sell them for and get some of the correct profile on there. Is the spare a 40 profile as well?

[Dezzy]

I ran 225x40x18's for well over 12 months before the 2 fronts were worn enough for me to warrant replacing them with 245x45x18. The only difference’s being she accelerated quicker and the speedo told lies, so I cocked up more miles than I had actually driven. Oh and the ride was terrible.
I wouldn't want to run one odd size tyre though.